The public transportation systems in some cities may allow passengers to enter a transit fare gate by using a mobile device (e.g., cell phone, personal digital assistant) that contains some form of an electronic transit fund card. An application in the transportation computer system may record the fare gate locations where a user entered and exited the transportation system and then use the information to calculate a fare. As transit fares are deducted from the user's transit fund account and the transit fund balance drops below a pre-defined level, a top-up request may be sent to the transportation payment system, which may communicate with a credit card company, to add funds to the transit fund balance associated with the mobile device.
The mobile device may communicate with a fare gate using a near field communication (NFC) transceiver if the mobile device is held in close proximity of the fare gate. The mobile device, in most scenarios, can also communicate with a wireless service provider server using a radio access network transceiver.